1. Field of the Invention
The present invention relates to an image transformation apparatus for performing a transformation processing for outputting a color image by an image output device such as a color printer, and an image transformation program storage medium storing an image transformation program which causes a computer system to operate as such an image transformation apparatus.
2. Description of the Related Art
Hitherto, to perform a color printing using a color printing machine, prior to performing the color printing, a proof image, which is closely similar in color to a color image to be printed by the color printing machine, is printed out using a color printer and the like. To produce such a proof image, the proof image is outputted in accordance with image data for a printer obtained such a manner that a printing profile describing a relation between image data and colors of the actual printed matter, associated with a sort of a printing machine to be used and use conditions of the printing machine (conditions necessary for a certain printing, including a sort of ink to be used and a material of paper; and a sort of a printing machine, is referred to as a printing condition), and a printer profile describing a relation between image data and colors of the actually outputted proof image, associated with a sort of a printer for outputting the proof image and use conditions of the printer (conditions necessary for outputting a certain proof image, including a sort of a printer, is referred to as a printer condition), are determined, and the image data for a printing is subjected to a color conversion processing in accordance with the printing profile and the printer profile and is converted into a data format representative of a halftone dot image adapted for a color printer used for outputting the proof image so that the image data for a printing is converted into the image data for a printer. Thus, it is possible to obtain a proof image which is coincident in color representation with the actual printed matter. Usually, a printing profile associated with a typical printing condition is provided from a printing service trader, and a printer for a proof image output is also provided from a maker of the printer.
The printing profile and the printer profile are stored in an image transformation apparatus, and are controlled so as to finally obtain a proof image of a preferable color representation. In the event that the printing image data is converted into the printer image data and is outputted, usually, the controlled printing profile and the proofer profile are combined to produce a single profile (a device link profile), so that a color conversion processing is applied to the printing image data referring to the device link profile. The image data subjected to the color conversion processing is converted into image data of a data format representative of a halftone dot image, which is adapted for a printer for outputting the proof image, and the image data thus converted is transmitted to the printer so that the printer outputs the proof image.
To output the proof image, the image translation apparatus receives raster image data from a so-called RIP (Raster Image Processor) system in which a color image produced and edited in a page description language is converted into a raster image data, and applies the color conversion processing and the conversion processing to the halftone dot image to the raster image data. With respect to the RIP system, there are known a plurality of types of RIP systems, such as an RIP system having a single function in which a color image described in a page description language is simply converted into a raster image data, and an RIP system having a function of performing the color conversion processing and the conversion processing to the halftone dot image directed to producing of the proof image, similar to the image transformation apparatus.
When it is considered that while such a plurality of types of RIP systems exist, the above-mentioned image transformation apparatus is used, it is possible to adapt the image transformation apparatus to a various type of RIP systems in accordance with such a manner that even if an RIP system is provided with a function of the color conversion processing and the conversion processing to the halftone dot image, a multiple gradation image, which is simply converted into a raster image data before those types of processing are applied, is received from the RIP system, and the color conversion processing and the conversion processing to the halftone dot image are carried out by the image transformation apparatus.
To perform the color conversion processing and the conversion processing to the halftone dot image, while various patterns exist also on halftone dots, it is known that while halftone dots for producing a proof image are selected from among halftone dot patterns which are prepared in the image transformation apparatus beforehand, a picture quality of a color image finally obtained is greatly effected by the selected halftone dot pattern. It is not ensured that the image transformation apparatus prepares the same halftone dot pattern as that adopted in the RIP system having a function of performing the halftone dot processing. When the RIP system has a function of performing the halftone dot processing, such a desire that the function of the halftone dot processing in the RIP system is used will be happened.
Even in the event that it is acceptable to adopt the halftone dot pattern which is not the same as the halftone dot pattern prepared in the RIP system, when the image translation apparatus receives from the RIP system image data representative of a multiple gradation image before the halftone dot processing, there is a need to process a very large capacity of image data to maintain an accuracy. This involves a gradation of the speed of processing.